This invention relates to circuit interrupters, and more specifically relates to circuit interrupters of the type in which an arc is drawn in a relatively stationary dielectric gas and the arc is then caused to rotate rapidly within the gas in order to cool the arc so it can extinguish at the next arc current zero.
Arc spinner type interrupters are known in the art and are typically shown in U.S. Pat. No. 4,052,577, in the name of Gerald A. Votta, as well as U.S. Pat. No. 4,052,576, in the name of Robert Kirkland Smith.
In circuit interrupters of the above type, an arc is drawn between a circular arc runner and a relatively movable contact which moves into and out of engagement with the arc runner. The disk-shaped arc runner is associated with a closely coupled series-connected, coaxial coil which carries the arcing current and which also induces a circulating current in the arc runner. The magnetic field produced by the circulating current in the arc runner and by the coil interact with the arc current in the arcing space to create a Lorentz force which tends to rotate or spin the arc around the arc runner and relative to the dielectric gas which fills the arc space. The relative motion between the arc and the gas then causes the cooling and deionization of the arc, to allow extinction of the arc at an arc current zero.
In prior art type constructions, it has been common that the current path through the relatively movable contact from the arc root point to the main current path has a radial segment relative to the central axis about which the arc rotates. This section was directed to produce a magnetic force on the arc root which tends to move the arc root on the movable contact radially outwardly. This can then lead to major restrikes across the main contacts since the main contacts are normally disposed radially outwardly of the arcing region. Moreover, this configuration causes a general loss of control of the arc position and of the arc length and increases the amount of arc energy which is applied to the gas.